“…The most important neoplasm a pathologist should exclude are ovarian cystadenoma (when confronted with a cystic struma), steroid cell tumours, carcinoid tumours, Sertoli-Leydig cell tumours, renal clear cell carcinoma, and metastatic melanoma (in case of oxyphilic struma) 2,4 . Differential diagnoses include: clear cell carcinoma (primary or metastatic from the kidney), primary or secondary hydatid cyst 6 , metastatic tumors from renal sarcoma 7 , endometrioid carcinomas, Sertoli cell tumour, hepatoid yolk sac tumour, malignant melanoma, serous cystadenoma, pregnancy lutcomas, metastatic thyroid carcinoma of the ovary 2,4 , secondary tumors from retroperitoneum 8,9 , GIST tumors 10,11 , primary 12 or secondary carcinoid tumors, tumoral or benign appendiceal pathology 13,14 .…”